* -b file = True if the file exists and is block special file. * -c file = True if the file exists and is character special file. * -d file = True if the file exists and is a directory. * -e file = True if the file exists. * -f file = True if the file exists and is a regular file * -g file = True if the file exists and the set-group-id bit is set. * -k file = True if the files' "sticky" bit is set. * -L file = True if the file exists and is a symbolic link. * -p file = True if the file exists and is a named pipe. * -r file = True if the file exists and is readable. * -s file = True if the file exists and its size is greater than zero. * -s file = True if the file exists and is a socket. * -t fd = True if the file descriptor is opened on a terminal. * -u file = True if the file exists and its set-user-id bit is set. * -w file = True if the file exists and is writable. * -x file = True if the file exists and is executable. * -O file = True if the file exists and is owned by the effective user id. * -G file = True if the file exists and is owned by the effective group id. * file1 –nt file2 = True if file1 is newer, by modification date, than file2. * file1 ot file2 = True if file1 is older than file2. * file1 ef file2 = True if file1 and file2 have the same device and inode numbers. * -z string = True if the length of the string is 0. * -n string = True if the length of the string is non-zero. * string1 = string2 = True if the strings are equal. * string1 != string2 = True if the strings are not equal. * !expr = True if the expr evaluates to false. * expr1 –a expr2 = True if both expr1 and expr2 are true. * expr1 –o expr2 = True is either expr1 or expr2 is true.

The syntax is :

arg1 OP arg2

where OP is one of –eq, -ne, -lt, -le, -gt, or –ge. Arg1 and arg2 may be positive or negative integers or the special expression "–l string" which evaluates to the length of string.

while [ 1 ]do statement(s)done

if [ ! -d /mnt ] # be sure the directory /mnt existsthen mkdir /mntfi

case $NUM of1) echo The number is 1 ;;2) echo The number is 2 ;;*) echo The number is not 1 or 2 ;;esac